Last year I did a similar trip to the one you outline,
comprising Madrid, Zaragoza, Tarragona (had been to Barca
previously), Valencia, Alicante (don't bother), Granada,
Seville, Cordoba and finishing up in Madrid again.

However, I did manage to get around without using the buses
at all - as a general rule I prefer trains. In my
experience, Spanish trains are comfortable and (reasonably)
punctual - but then I am used to Swiss punctuality!!

What I can tell you is the AVE from Seville to Madrid which
stops at Cordoba is quick and comfortable. I am informed
that if the AVE is more than five minutes late you are
entitled to a refund - I am also informed that this rarely
happens and my trips on the AVE arrived at the destination
early. A statistical ploy perhaps or just good service?
Either way, it's worth the money and I suspect it would be a
whole heap quicker than taking the bus - but you would have
to check this as I don't know.

With regards to Granda, I assume you will be visiting the
UNESCO-listed Al-Hambra (http://www.alhambra.org/) For the
Al-Hambra visit, I strongly recomend that you purchase your
entry ticket in advance, which can be done either online or
in person at any BBVA bank nationwide in Spain. Number of
tickets for entry each day are limited (7,000 at the time of
my visit) with around 1,500 on sale at the door each day.
The wait to get your ticket on the door can be a painful
three or four hours (as I know from personal experience)
with some people queuing from as early as six or six-thirty
in the morning.

With regards to location of train stations the main train
stations in Madrid are centrally located and connected to
the underground (metro) train system so you shouldn't have a
problem getting around. The station at Cordoba is somewhat
out of the way for the main attractions, and I would
recomend staying closer to the centre for the conveniance of
your feet - a taxi to my hotel cost around 15E/20E, iirc.
Ditto Seville, although the cab was more expensive as I was
staying some distance from the station, but quite centrally.

I don't know if you would be interested in bullfights at all
but as you are visiting Andalucia, a bull-fighting
heartland, there was quite a discussion about this during
last year so you might want to check the archives. If you do
decide to go, I would recomend that you do so in Seville.

When in Madrid, I strongly suggest that you take a tour of
the Royal Palace, which is an absolute gem and, when in
Madrid, utterly unmissable. If you are into a bit of Art the
three museums of Museo Nacional del Prado (
http://museoprado.mcu.es/) and Museo Nacional Centro de Arte
Reina Sofia (http://museoreinasofia.mcu.es/) and Museo
Thyssen-Bornemisza (http://www.museothyssen.org/) are world
class.